In the Maftet region, a block of material to the right has a similar shape and appearance to the depression on the left. The block is around 100 m in diameter, and the pit is around 150 m across. One theory is that this is evidence of surface disruption and material ejection produced by subsurface gas pressure build-up of a super-volatile such as carbon monoxide or carbon dioxide. However, the proposal needs to overcome the high porosity of the nucleus and explain how gas can be trapped in a pocket so that pressure can build. Mechanisms producing subsurface ice barriers (through volatile transport to colder areas within the nucleus) need to be considered.
A labelled version of this image is available here.
Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA